DECLARE FILTER
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Declares an existing Blob filter to a database. Available in gpre, DSQL, and isql.
DECLARE FILTER filter
INPUT_TYPE subtype OUTPUT_TYPE subtype
ENTRY_POINT 'entryname' MODULE_NAME 'modulename';
In SQL statements passed to DSQL, omit the terminating semicolon. In embedded applications written in C and C++, and in
isql, the semicolon is a terminating symbol for the statement, so it must be included.| Argument | Description |
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<filter> |
Name of the filter; must be unique among filter names in the database. |
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Specifies the Blob subtype from which data is to be converted. |
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Specifies the Blob subtype into which data is to be converted. |
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‘<entryname>’ |
Quoted string specifying the name of the Blob filter as stored in a linked library. |
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‘<modulename>’ |
Quoted file specification identifying the object module in which the filter is stored. |
Description: DECLARE FILTER provides information about an existing Blob filter to the database: where to find it, its name, and the Blob subtypes it works with. A Blob filter is a user-written program that converts data stored in Blob columns from one subtype to another.
INPUT_TYPE and OUTPUT_TYPE together determine the behavior of the Blob filter. Each filter declared to the database should have a unique combination of INPUT_TYPE and OUTPUT_TYPE integer values. InterBase provides a built-in type of 1, for handling text. User-defined types must be expressed as negative values.
<entryname> is the name of the Blob filter stored in the library. When an application uses a Blob filter, it calls the filter function with this name.
Example: The following isql statement declares a Blob filter:
DECLARE FILTER DESC_FILTER
INPUT_TYPE 1
OUTPUT_TYPE -4
ENTRY_POINT 'desc_filter'
MODULE_NAME 'FILTERLIB';